This invention relates to centrifugal separators for separating contaminants from contaminated fluids, and particularly for extracting solid matter from oil or other fluids or for separating a heavier fluid from a lighter fluid (for example, water from fuel oil). Such separators include a rotatable drum through which fluid is fed so that during the period when a part of the fluid remains in the drum it is subjected to centrifugal action caused by the rotation. This causes solid matter in the fluid or the heavier of the two fluids to be separated and be retained around the circumferential wall of the drum while the "cleaned" fluid is taken to where it is required for use. The drum is provided with one or more outlet nozzles through which fluid leaves the interior of the drum, the fluid issuing from the nozzles with a substantially tangential component with respect to the drum whereby the drum is caused to rotate by the reaction of the jets of fluid issuing from the nozzles. Subsequently such a centrifugal separator will be referred to as of the kind described.
The invention has particular application to the cleaning of lubricating oil in internal combustion engines. Although centrifugal separators of conventional type have been used for this purpose, oil filters are more widely employed. However conventional fluid filters, such as oil filters having paper elements, are basically mechanical strainers which include a filter element having pores which trap and segregate dirt from the fluid. Since the flow through the filter is a function of the poe size, filter flow will decrease as the filter pack becomes clogged with dirt. As the filtration system must remove dirt at the same rate at which the dirt enters the oil, a clogged conventional paper element filter cannot process enough oil to keep the dirt level of the oil at a satisfactory level. A further disadvantage of some mechanical strainer type filters is that they tend to remove oil additives. Furthermore, the additives may be depleted to some extent by acting upon trapped dirt in the filter instead of on a working surface of an engine as intended.
Conventional centrifugal separators of the kind referred to must be dismantled for cleaning out the drum when it is nearly full of contaminants. This cleaning process is not only tedious and dirty but involves a relatively expensive construction of drum capable of being repeatedly readily opened up for cleaning and readily reassembled with tightly sealed joints.
Thus while centrifugal separators have an undoubtably superior performance to element type filters the need to be cleaned out has up till now necessitated a complicated construction with relatively heavy machined castings so that it will stand up to periodic cleaning to remove the sludge built up. This has probably militated against the more universal use of centrifugal separators in engines. It has also not been possible to provide an effective warning system to show that the drum is full which further complicates the problem of maintenance.